The background of the present invention, insofar as its use in the printing field is concerned, is provided by the disclosure in said copending application, Ser. No. 39,372, referred to above. The background presented by the microballistic printer of said copending application presents the need for a resilient breech having an extremely long service life under operation at cyclic rates which may range from 1,000 to 2,000 per second. In such microballistic printer, the projectiles are spheres or balls of metal which are presented successively to a breech having a passageway which includes a sphincter or restriction made of a resilient plastic material. Each successive projectile is brought to the breech under mechanical force, and gaseous pressure is built up in a chamber behind the projectile during the time required for the projectile to be mechanically forced through the restriction. After passing the restriction, the projectile is released into the gun barrel for travel and discharge under gaseous pressure. Incident to the forcing of each projectile through the breech restriction, the resilient material is subjected to some frictional wear and is distorted to permit the passage of the projectile therethrough. While the resilient materials from which such a breech may be made have afforded a service life of several hundred million discharges, it is desirable that a breech be provided that will have a much greater service life.